The effect of macromolecular crowding on the kinetics and equilibria of biochemical reactions has been postulated to be of general significance (Minton, Biopolymers 20: 2093-2120, 1981). In vivo, these reactions occur in the presence of very high concentrations of non-specific background macromolecules termed "volume excluders", which do not appear to directly participate in the reaction, but which may theoretically affect the thermodynamic activity and conformational equilibria of a variety of reaction systems.
Consistent with this theory are a number of studies reporting an alteration of in vitro behavior of biological systems in the presence of high concentrations of polymers as volume excluders. Exemplary is the reported acceleration of renaturation of DNA in the presence of volume-excluding inert polymers (Wieder, et al, Biopolymers 20: 1537-1547, 1981), and the reported use of highly concentrated polymer solutions to effect a conformational change in DNA derived from T.sub.4 and T.sub.7 bacteriophage (Lerman, Proc. Natl. Acad. Sci. 68: 1886-1890, 1971).